CVE-2021-43793 in Discourse
Summary
by MITRE • 12/01/2021
Discourse is an open source discussion platform. In affected versions a vulnerability in the Polls feature allowed users to vote multiple times in a single-option poll. The problem is patched in the latest tests-passed, beta and stable versions of Discourse
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Analysis
by VulDB Data Team • 12/08/2021
The vulnerability identified as CVE-2021-43793 affects Discourse, an open source discussion platform widely used for community forums and online discussions. This security flaw resides within the Polls feature implementation and represents a significant issue that undermines the integrity of polling mechanisms within the platform. The vulnerability specifically targets single-option polls where users should theoretically be restricted to casting only one vote, yet the flaw permits multiple voting attempts, effectively compromising the democratic nature of polling systems. This issue impacts the fundamental trust users place in the platform's ability to maintain accurate and fair voting processes, particularly in community-driven environments where consensus building and decision making rely on poll outcomes.
The technical root cause of this vulnerability stems from inadequate input validation and access control mechanisms within the polls feature implementation. When users interact with single-option polls, the system fails to properly enforce voting restrictions that should prevent duplicate submissions. This flaw likely occurs due to insufficient session tracking or state management during vote processing, allowing malicious or exploitative users to bypass intended limitations. The vulnerability demonstrates a classic lack of proper authorization checks and input sanitization, which aligns with common software security weaknesses documented in CWE categories related to insufficient validation of inputs and improper access control. The issue represents a failure in the platform's defensive programming practices, where the system does not adequately verify that a user has not already cast their vote in a given poll.
The operational impact of CVE-2021-43793 extends beyond simple voting manipulation and represents a broader threat to community integrity and platform credibility. When users can vote multiple times, the results of polls become skewed and unreliable, potentially leading to incorrect decisions being made by community members who rely on these outcomes for governance or content moderation. This vulnerability particularly affects platforms where polls are used for important decisions such as feature requests, content policies, or community guidelines. The security implications also extend to potential abuse scenarios where malicious actors could artificially inflate support for certain proposals or undermine legitimate community preferences. From a cyber threat perspective, this vulnerability could be exploited as part of broader attack campaigns targeting community platforms, especially when combined with other weaknesses that might allow for account manipulation or session hijacking. The vulnerability's classification aligns with ATT&CK techniques related to privilege escalation and resource consumption through manipulation of voting systems.
Organizations and community managers using Discourse platforms should prioritize immediate remediation by upgrading to the latest stable, beta, or tests-passed versions that contain the patched implementation. The vulnerability's resolution involves proper state management and session validation that ensures each user can only cast one vote per poll, regardless of the number of attempts they make. Security teams should also consider implementing additional monitoring for unusual voting patterns that might indicate exploitation attempts. The patch addresses the core issue through enhanced input validation and access control mechanisms, ensuring that voting systems maintain their integrity and reliability. Organizations should conduct thorough testing of their Discourse installations to confirm that the vulnerability has been properly resolved and that legitimate users can no longer exploit the multiple voting capability. This remediation process should be integrated into regular security maintenance procedures to prevent similar vulnerabilities from emerging in other platform features. The fix demonstrates the importance of proper software development practices and the necessity of thorough testing for all interactive features, particularly those involving user participation and decision making.